This study is intended to provide further information on the multiple factors inducing irreversible myocardial damage during ischemia. The major technique to be used is phosphorus nuclear magnetic resonance which can non-invasively monitor tissue pH and the concentrations of ATP, ADP, phosphocreatine, orthophosphate, and other phosphorus containing metabolites within the cell. These compounds provide a metabolic picture of the normal and ischemic myocardium which can be correlated to functional data. Left ventricular pressure will be measured under all experimental conditions. In addition, attempts will be made to prepare two and three dimensional images of the heart based on its phosphorus NMR properties. The NMR data will be verified by comparison to similar information obtained by other methods including chemical analysis and pathological experimentation by light and electron microscopy. These data will be used to guide the development of improved procedures for the protection and preservation of ischemic myocardium during clinical conditions of acute myocardial infarction, cardiac insufficiency and cardiac arrest. Furthermore, the NMR techniques will facilitate the development of an effective cardioplegic and reperfusion regimen to minimize myocardial damage during surgical procedures such as the saphaneous vein graft bypass protocol.